Re: [PATCH 5/6] cfg80211: Fix regression with 11d on bands

[Johannes Berg <johannes@sipsolutions.net>]

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On Wed, 2009-01-07 at 17:43 -0800, Luis R. Rodriguez wrote:
> This fixes a regression on disallowing bands introduced with the new
> 802.11d support. The issue is that IEEE-802.11 allows APs to send
> a subset of what a country regulatory domain defines. This was clarified
> in this document:
> 
> http://tinyurl.com/11d-clarification

I think you should give the full link, regardless of how long it is.
It's just on the 802 docserver, no?

> As such it is possible, and this is what is done in practice, that a
> single band 2.4 GHz AP will only send 2.4 GHz band regulatory information
> through the 802.11 country information element and then the current
> intersection with what CRDA provided yields a regulatory domain with
> no 5 GHz information -- even though that country may actually allow
> 5 GHz operation. We correct this by only applying the intersection rules
> on a channel if the the intersection yields a regulatory rule on the
> same band the channel is on.

Seems sane to me.

> Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>

Acked-by: Johannes Berg <johannes@sipsolutions.net>

> ---
>  net/wireless/reg.c |   77 ++++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 files changed, 75 insertions(+), 2 deletions(-)
> 
> diff --git a/net/wireless/reg.c b/net/wireless/reg.c
> index 3d56a1d..bea98ed 100644
> --- a/net/wireless/reg.c
> +++ b/net/wireless/reg.c
> @@ -421,6 +421,31 @@ static u32 freq_max_bandwidth(const struct ieee80211_freq_range *freq_range,
>  	return 0;
>  }
>  
> +/**
> + * freq_in_rule_band - tells us if a frequency is in a frequency band
> + * @freq_range: frequency rule we want to query
> + * @freq_khz: frequency we are inquiring about
> + *
> + * This lets us know if a specific frequency rule is or is not relevant to
> + * a specific frequency's band. Bands are device specific and artificial
> + * definitions (the "2.4 GHz band" and the "5 GHz band"), however it is
> + * safe for now to assume that a frequency rule should not be part of a
> + * frequency's band if the start freq or end freq are off by more than 2 GHz.
> + * This resolution can be lowered and should be considered as we add
> + * regulatory rule support for other "bands".
> + **/
> +static bool freq_in_rule_band(const struct ieee80211_freq_range *freq_range,
> +	u32 freq_khz)
> +{
> +#define ONE_GHZ_IN_KHZ	1000000
> +	if (abs(freq_khz - freq_range->start_freq_khz) <= (2 * ONE_GHZ_IN_KHZ))
> +		return true;
> +	if (abs(freq_khz - freq_range->end_freq_khz) <= (2 * ONE_GHZ_IN_KHZ))
> +		return true;
> +	return false;
> +#undef ONE_GHZ_IN_KHZ
> +}
> +
>  /* Converts a country IE to a regulatory domain. A regulatory domain
>   * structure has a lot of information which the IE doesn't yet have,
>   * so for the other values we use upper max values as we will intersect
> @@ -753,11 +778,19 @@ static u32 map_regdom_flags(u32 rd_flags)
>   * a given wireless device. If the device has a specific regulatory domain
>   * it wants to follow we respect that unless a country IE has been received
>   * and processed already.
> + *
> + * Returns 0 if it was able to find a valid regulatory rule which does
> + * apply to the given center_freq otherwise it returns non-zero. It will
> + * also return -ERANGE if we determine the given center_freq does not even have
> + * a regulatory rule for a frequency range in the center_freq's band. See
> + * freq_in_rule_band() for our current definition of a band -- this is purely
> + * subjective and right now its 802.11 specific.
>   */
>  static int freq_reg_info(struct wiphy *wiphy, u32 center_freq, u32 *bandwidth,
>  			 const struct ieee80211_reg_rule **reg_rule)
>  {
>  	int i;
> +	bool band_rule_found = false;
>  	const struct ieee80211_regdomain *regd;
>  	u32 max_bandwidth = 0;
>  
> @@ -780,7 +813,15 @@ static int freq_reg_info(struct wiphy *wiphy, u32 center_freq, u32 *bandwidth,
>  		rr = &regd->reg_rules[i];
>  		fr = &rr->freq_range;
>  		pr = &rr->power_rule;
> +
> +		/* We only need to know if one frequency rule was
> +		 * was in center_freq's band, that's enough, so lets
> +		 * not overwrite it once found */
> +		if (!band_rule_found)
> +			band_rule_found = freq_in_rule_band(fr, center_freq);
> +
>  		max_bandwidth = freq_max_bandwidth(fr, center_freq);
> +
>  		if (max_bandwidth && *bandwidth <= max_bandwidth) {
>  			*reg_rule = rr;
>  			*bandwidth = max_bandwidth;
> @@ -788,6 +829,9 @@ static int freq_reg_info(struct wiphy *wiphy, u32 center_freq, u32 *bandwidth,
>  		}
>  	}
>  
> +	if (!band_rule_found)
> +		return -ERANGE;
> +
>  	return !max_bandwidth;
>  }
>  
> @@ -812,8 +856,37 @@ static void handle_channel(struct wiphy *wiphy, enum ieee80211_band band,
>  		&max_bandwidth, &reg_rule);
>  
>  	if (r) {
> -		flags |= IEEE80211_CHAN_DISABLED;
> -		chan->flags = flags;
> +		/* This means no regulatory rule was found in the country IE
> +		 * with a frequency range on the center_freq's band, since
> +		 * IEEE-802.11 allows for a country IE to have a subset of the
> +		 * regulatory information provided in a country we ignore
> +		 * disabling the channel unless at least one reg rule was
> +		 * found on the center_freq's band. For details see this
> +		 * clarification:
> +		 *
> +		 * http://tinyurl.com/11d-clarification
> +		 */
> +		if (r == -ERANGE &&
> +		    last_request->initiator == REGDOM_SET_BY_COUNTRY_IE) {
> +#ifdef CONFIG_CFG80211_REG_DEBUG
> +			printk(KERN_DEBUG "cfg80211: Leaving channel %d MHz "
> +				"intact on %s - no rule found in band on "
> +				"Country IE\n",
> +				chan->center_freq, wiphy_name(wiphy));
> +#endif
> +		} else {
> +		/* In this case we know the country IE has at least one reg rule
> +		 * for the band so we respect its band definitions */
> +#ifdef CONFIG_CFG80211_REG_DEBUG
> +			if (last_request->initiator == REGDOM_SET_BY_COUNTRY_IE)
> +				printk(KERN_DEBUG "cfg80211: Disabling "
> +					"channel %d MHz on %s due to "
> +					"Country IE\n",
> +					chan->center_freq, wiphy_name(wiphy));
> +#endif
> +			flags |= IEEE80211_CHAN_DISABLED;
> +			chan->flags = flags;
> +		}
>  		return;
>  	}
>  

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